1. Field of the Invention
The present invention relates to a machine for single sided or double sided application of a liquid or viscous coating medium by way of at least one applicator device onto the surface of a moving material web, especially a paper or cardboard web.
2. Description of the Related Art
With a view to guaranteeing good coating results that meet high quality standards, the various components of the referenced machinery, as well as the coating medium collecting device are subject to a multitude of requirements. Considering that the curtain or veil should not be too high, in other words, that the dispensing opening arrangement is not too high above the moving background, the medium collecting device should be constructed comparatively compactly, especially with regard to its height. On the other hand, a methodical removal of the collected medium through the collecting device must be ensured. This can be difficult, especially with highly viscous mediums and/or very wide machines and under conventional projections may only be possible with the acceptance of a high curtain height.
The addressed requirements are obviously competing with each other. The problem can be alleviated somewhat by making the coating application onto a material web segment that inclines or drops off in the direction of web travel and in that the coating medium is removed at least initially, in the direction of web travel, or in the direction opposite to web travel. In spite of this, the problem of accepting and releasing the curtain or veil through the medium collecting device as closely as possible above the moving background, especially the material web surface, remains in order to avoid or at least reduce contraction of the released or severed curtain, so that the background is not treated with undefined coating medium, especially coating medium drops. What is needed in the art is an improvement in this area.
In a narrower context of the previously cited problem an additional requirement arises in that, to pick up the curtain or veil in order to interrupt the application process, or to release it to start the application process through elements of a suitably formed edge so that an undefined treatment of the moving background, especially the moving material web with coating medium is avoided. With conventional coating medium collection devices that are in the embodiment of pans or troughs (so-called “starter troughs”) that extend across the material web, a situation may arise where the curtain may run off a wall of the starter trough due to adhesion and surface tension effects in the manner of the well known “tea pot effect” and drip from the wall in an undefined fashion onto the background. This type of coating medium run-off from surface segments of the medium collecting device should be avoided. What is needed in the art is an improvement in this area.
With machinery of the referenced type, clean-up of components and surfaces which are in contact with the coating medium is generally an issue. This also applies especially to the coating medium collecting device. Since this type of machinery is often subject to space restrictions in direction of web travel, as well as to height restrictions this denotes that only limited space is usually available for the provided “curtain nozzle” and the medium collecting device allocated to the nozzle. This frequently results in difficult access to the medium collecting device for clean-up purposes. In addition it is desirable if a quasi-automatic clean-up process without the direct intervention of the operating personnel upon the components that are to be cleaned is possible. What is needed in the art is to render possible an effective clean-up method for the medium collecting device.